FIG. 1 is a schematic diagram of the exposure process for an existing large area semi-transmitting mask. As shown in the figure, the large area semi-transmitting mask comprises a non-transmitting region A covered by metal Cr, a semi-transmitting region B, and a full transmitting region C. Photoresists 5 are shaped with different thicknesses at the underlying layer after an exposure process with the conventional semi-transmitting mask.
FIG. 2 is a schematic diagram of the distribution of the photoresists on the substrate as shown in FIG. 1 after a development process. As shown in the figure, the thickness of the unexposed photoresist 5 corresponding to the non-transmitting region A is D, the thickness of the photoresist 5 corresponding to the semi-transmitting region B is d, and the reference numeral 60 denotes a via pattern formed in the full transmitting region C.
After the exposure and development of the substrate, the photoresist 5 surrounding the formed via 60 is the photoresist 5 corresponding to the semi-transmitting region. In the exposure process, the region of the photoresist 5 where the via 60 is to be formed is affected by the intensity of the ultraviolet light 3 in the vicinity of the region, such that the size of the via 60 finally formed is affected significantly. Since the intensity of the ultraviolet light 3 in the vicinity of the via 60 results directly in a change in the thickness of the photoresist 5 surrounding the via 60, the size of the via 60 is shown to be affected significantly by the change in the thickness of the photoresist 5 surrounding the via 60.